In the list of organisms given below, those that reproduce by the asexual method are
(i) banana
(ii) dog
(iii) yeast
(iv) Amoeba
i and iv
i, iii and iv
i and iv
ii, iii and iv
In a flower, the parts that produce male and female gametes (germ cells) are
stamen and anther
filament and stigma
anther and ovary
stamen and style
Which of the following is the correct sequence of events of sexual reproduction in a flower?
pollination, fertilisation, seedling, embryo
seedling, embryo, fertilisation, pollination
pollination, fertilisation, embryo, seedling
embryo, seedling, pollination, fertilisation
Offspring formed by asexual method of reproduction have greater similarity among themselves because
(i) asexual reproduction involves only one parent
(ii) asexual reproduction does not involve gametes
(iii) asexual reproduction occurs before sexual reproduction
(iv) asexual reproduction occurs after sexual reproduction
i and ii
i and iii
i and iv
ii and iv
Characters transmitted from parents to offspring are present in
cytoplasm
ribosome
golgi bodies
genes
Characters that are transmitted from parents to offspring during reproduction show
only similarities with parents
only variations with parents
both similarities and variations with parents
neither similarities nor variations
A feature of reproduction that is common to Amoeba, Spirogyra and Yeast is that
they reproduce asexually
they are all unicellular
they reproduce only sexually
they are all multicellular
In Spirogyra, asexual reproduction takes place by
breaking up of filaments into smaller bits
division of a cell into two cells
division of a cell into many cells
formation of young cells from older cells
The ability of a cell to divide into several cells during reproduction in Plasmodium is called
budding
reduction division
binary fission
multiple fission
The correct sequence of reproductive stages seen in flowering plants is
gametes, zygote, embryo, seedling
zygote, gametes, embryo, seedling
seedling, embryo, zygote, gametes
gametes, embryo, zygote, seedling
The number of chromosomes in parents and offspring of a particular species remains constant due to
doubling of chromosomes after zygote formation
halving of chromosomes during gamete formation
doubling of chromosomes after gamete formation
halving of chromosomes after gamete formation
In Rhizopus, tubular thread-like structures bearing sporangia at their tips are called
filaments
hyphae
rhizoids
roots
Vegetative propagation refers to formation of new plants from
stem, roots and flowers
stem, roots and leaves
stem, flowers and fruits
stem, leaves and flowers
Factors responsible for the rapid spread of bread mould on slices of bread are
(i) large number of spores
(ii) availability of moisture and nutrients in bread
(iii) presence of tubular branched hyphae
(iv) formation of round shaped sporangia
i and iii
ii and iv
i and ii
iii and iv
Length of pollen tube depends on the distance between
pollen grain and upper surface of stigma
pollen grain on upper surface of stigma and ovule
pollen grain in anther and upper surface of stigma
upper surface of stigma and lower part of style
Which of the following statements are true for flowers?
(i) Flowers are always bisexual
(ii) They are the sexual reproductive organs
(iii) They are produced in all groups of plants
(iv) After fertilisation they give rise to fruits
i and iv
ii and iii
i and iii
ii and iv
Which among the following statements are true for unisexual flowers?
(i) They possess both stamen and pistil
(ii) They possess either stamen or pistil
(iii) They exhibit cross pollination
(iv) Unisexual flowers possessing only stamens cannot produce fruits
i and iv
ii, iii and iv
iii and iv
i, iii and iv
Which among the following statements are true for sexual reproduction in flowering plants?
(i) It requires two types of gametes
(ii) Fertilisation is a compulsory event
(iii) It always results in formation of zygote
(iv) Offspring formed are clones
(i) and (iv)
(i), (ii) and (iv)
(i), (ii) and (iii)
(ii), (iii) and (iv)
In Figure 8.1, the parts A, B and C are sequentially
cotyledon, plumule and radicle
plumule, radicle and cotyledon
plumule, cotyledon and radicle
radicle, cotyledon and plumule
Offspring formed as a result of sexual reproduction exhibit more variations because
sexual reproduction is a lengthy process
genetic material comes from two parents of the same species
genetic material comes from two parents of different species
genetic material comes from many parents
Reproduction is essential for living organisms in order to
keep the individual organism alive
fulfill their energy requirement
maintain growth
continue the species generation after generation
During adolescence, several changes occur in the human body. Mark one change associated with sexual maturation in boys
loss of milk teeth
increase in height
cracking of voice
weight gain
In human females, an event that reflects onset of reproductive phase is
growth of body
changes in hair pattern
change in voice
menstruation
In human males, the testes lie in the scrotum, because it helps in the
process of mating
formation of sperm
easy transfer of gametes
all the above
Which among the following is not the function of testes at puberty?
(i) formation of germ cells
(ii) secretion of testosterone
(iii) development of placenta
(iv) secretion of estrogen
(i) and (ii)
(ii) and (iii)
(iii) and (iv)
(i) and (iv)
The correct sequence of organs in the male reproductive system for transport of sperms is
testis → vas deferens → urethra
testis → ureter → urethra
testis → urethra → ureter
testis → vas deferens → ureter
Which among the following diseases is not sexually transmitted?
Syphillis
Hepatitis
HIV - AIDS
Gonorrhoea
In a bisexual flower, in spite of the young stamens being removed artificially, the flower produces fruit. Provide a suitable explanation for this situation.
The pistil remains intact and cross pollination occurs, leading to fertilisation and formation of fruit.
Can you consider cell division as a type of reproduction in unicellular organisms? Give one reason.
Yes, because cell division forms two daughter cells, resulting in the production of more individuals of the organism.
What is a clone? Why do offsprings formed by asexual reproduction exhibit remarkable similarity?
A clone is an offspring of an organism formed by asexual reproduction. They exhibit remarkable similarity because they possess exact copies of the DNA of their parent.
Explain how offsprings and parents of organisms reproducing sexually have the same number of chromosomes.
Reduction division (meiosis) during gamete formation halves the chromosome number in both male and female gametes. When these gametes fuse during fertilisation, the original number of chromosomes is restored in the offspring.
Colonies of yeast fail to multiply in water, but multiply in sugar solution. Give one reason for this.
Sugar provides energy for sustaining all life activities in yeasts. In water, they fail to reproduce due to inadequate energy in their cells.
Why does bread mould grow profusely on a moist slice of bread rather than on a dry slice?
Moisture is essential for the growth of hyphae. A moist bread slice offers moisture and nutrients, enabling the mould to grow profusely. A dry slice offers nutrients but lacks moisture, preventing hyphal growth.
Give two reasons for the appearance of variations among the progeny formed by sexual reproduction.
Sexual reproduction involves two parents with different sets of characters.
The gene combinations are different in gametes.
Would a Planaria cut vertically into two halves regenerate into two individuals? Complete the diagram by indicating the regenerated regions.
Yes. The shaded regions in Figures D and E represent the regenerated halves.
Gather information about chromosome numbers of some animals and plants. Correlate the number with the size of organism and answer the questions.
(a) Do larger organisms have more chromosomes?
(b) Can organisms with fewer chromosomes reproduce more easily?
(c) Justify: More chromosomes mean greater DNA content.
(a) There is no relationship between size of organism and its chromosome number.
(b) No. Reproduction follows a common pattern and is not dependent on chromosome number.
(c) Since chromosomes contain DNA, more chromosomes indicate more DNA quantity.
In tobacco plant, the male gametes have twenty-four chromosomes. What is the number of chromosomes in the female gamete and in the zygote?
The female gamete has 24 chromosomes and the zygote has 48 chromosomes.
Why cannot fertilisation take place in flowers if pollination does not occur?
Fertilisation requires both male and female gametes. If pollination does not occur, the male gamete is not available, hence fertilisation cannot take place.
Is the chromosome number of zygote, embryonal cells, and adult of an organism always constant? How is this constancy maintained?
Yes. The constancy is maintained because cells in all these stages undergo mitotic divisions, preserving chromosome number.
Where is the zygote located in the flower after fertilisation?
The zygote is located inside the ovule present in the ovary.
Reproduction is linked to stability of population of a species. Justify.
DNA is copied from one generation to the next with high consistency and minor variations, leading to stability of species.
How are general growth and sexual maturation different from each other?
General growth refers to overall physical development such as increase in height and weight. Sexual maturation is specific to puberty-related changes such as cracking of voice, new hair patterns, and development of breasts in females.
Trace the path of sperm during ejaculation and mention the glands involved and their functions.
Sperms travel from testes into the vas deferens and then enter the urethra before ejaculation. Secretions of seminal vesicles and prostate gland provide nutrition and aid sperm transport.
What changes are observed in the uterus if fertilisation does not occur?
The thick and spongy lining of the uterus breaks and comes out through the vagina as blood and mucus.
What changes are observed in the uterus subsequent to implantation of the young embryo?
The uterine wall thickens and becomes richly supplied with blood. Placenta develops to provide nutrients and oxygen to the embryo.
What are the benefits of using mechanical barriers during sexual act?
Mechanical barriers like condoms prevent sperms from reaching the egg, avoiding pregnancy. They also prevent transmission of infections.
In the given diagram, label the parts and mention their functions.
(a) Ovary – Production of egg
(b) Oviduct – Site of fertilisation
(c) Uterus – Site of implantation
(d) Vagina – Entry of sperms
What is the ratio of chromosome number between an egg and its zygote? How is a sperm genetically different from an egg?
The ratio is 1:2. Sperms contain either an X or Y chromosome, whereas an egg always has an X chromosome.
Why are budding, fragmentation and regeneration all considered as asexual types of reproduction? With neat diagrams explain the process of regeneration in Planaria.
Budding, fragmentation and regeneration are considered asexual types of reproduction because each of them involves only one parent and gametes are not involved. The offspring produced are genetically identical to the parent because they arise from mitotic cell division.
Regeneration in Planaria
Planaria has a remarkable ability to regenerate. When the organism is cut vertically or horizontally, each piece can grow and develop into a complete individual. This is possible because specialized cells present in the organism divide rapidly to form large numbers of cells, which then differentiate into various tissues and organs.
Steps of Regeneration
Diagram Description: The regenerated regions in pieces D and E show the formation of missing body parts such as the head or tail, depending on the fragment.
Write two points of difference between asexual and sexual types of reproduction. Describe why variations are observed in the offspring formed by sexual reproduction.
Differences between Asexual and Sexual Reproduction
| Asexual Reproduction | Sexual Reproduction |
|---|---|
| (a) Involves only one parent. | (i) Involves two parents. |
| (b) Gametes are not produced. | (ii) Gametes are produced. |
| (c) No fertilisation or zygote formation occurs. | (iii) Fertilisation and zygote formation occur. |
| (d) Meiosis does not occur during reproduction. | (iv) Meiosis occurs at the time of gamete formation. |
Reason for Variations in Sexual Reproduction
During sexual reproduction, male and female gametes fuse. Although the gametes have the same number of chromosomes, their DNA is not identical. The recombination and assortment of genes during meiosis lead to genetic variations. When these gametes fuse during fertilisation, the resulting offspring inherits a unique combination of genes, resulting in variations.
Distinguish between pollination and fertilisation. Mention the site and product of fertilisation in a flower. Draw a neat, labelled diagram of a pistil showing pollen tube growth and its entry into the ovule.
Difference between Pollination and Fertilisation
Site of fertilisation: Ovule
Product of fertilisation: Zygote
Pistil Diagram Description: The pistil consists of stigma, style and ovary. After pollination, the pollen grain germinates on the stigma and forms a pollen tube. The pollen tube grows through the style and reaches the ovary, finally entering the ovule where fertilisation takes place.
Distinguish between a gamete and a zygote. Explain their roles in sexual reproduction.
Difference between Gamete and Zygote
Roles in Sexual Reproduction
Gametes carry genetic material from parents. When the male and female gametes fuse during fertilisation, the zygote is formed. The zygote undergoes repeated mitotic divisions to develop into an embryo, eventually forming a new individual. The zygote inherits the characteristics of both parents.
Draw the diagram of a flower and label the four whorls. Write the names of gamete producing organs in the flower.
Four Whorls of a Flower: Calyx, Corolla, Androecium, Gynoecium.
Gamete-producing organs:
Diagram Description: The flower shows clearly labelled calyx, corolla, androecium and gynoecium with reproductive organs including anther and ovary.
What is placenta? Mention its role during pregnancy.
The placenta is a special tissue connection between the embryo and the uterine wall. It contains villi that increase the surface area for exchange.
Role of Placenta
What are various ways to avoid pregnancy? Elaborate any one method.
Various contraceptive methods include mechanical methods, chemical methods, and surgical methods.
Example: Mechanical Method
Mechanical barriers such as condoms prevent the sperm from entering the female reproductive tract. This avoids fertilisation because the sperm cannot reach the egg. Condoms also prevent the transmission of sexually transmitted infections.
How does fertilisation take place? Fertilisation occurs once in a month. Comment.
Process of Fertilisation:
Why fertilisation occurs once a month:
The ovary releases one egg approximately every month. If the egg is not fertilised, it degenerates and menstruation occurs. Therefore, fertilisation can occur only during the period when the egg is available.
Reproduction is essentially a phenomenon that is not for survival of an individual but for the stability of a species. Justify.
Reproduction ensures the continuity of a species by producing new individuals. Although an individual organism may not need reproduction for its own survival, the species as a whole depends on it.
Justification:
Describe sexually transmitted diseases and mention the ways to prevent them.
Sexually transmitted diseases (STDs) are infectious diseases spread through sexual contact. They may be caused by bacteria or viruses.
Common STDs: Syphilis, Gonorrhoea, HIV-AIDS
Prevention: